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| author | Quim Muntal <quimmuntal@gmail.com> | 2020-10-22 22:32:20 +0200 |
|---|---|---|
| committer | Austin Clements <austin@google.com> | 2020-11-02 00:46:44 +0000 |
| commit | e463c28cc116fb1f40a4e203bddf93b6ef52c8d9 (patch) | |
| tree | c95ad0a618c0fd9882d4e2cc9914ec5cc7c73813 /src/cmd | |
| parent | 333d2010ec98aaea244b65b7bc4d7d80c71e21b1 (diff) | |
| download | go-e463c28cc116fb1f40a4e203bddf93b6ef52c8d9.tar.xz | |
cmd/link: avoid exporting all symbols on windows buildmode=pie
Marking one functions with __declspec(dllexport) forces mingw to
create .reloc section without having to export all symbols.
See https://insights.sei.cmu.edu/cert/2018/08/when-aslr-is-not-really-aslr---the-case-of-incorrect-assumptions-and-bad-defaults.html for more info.
This change cuts 73kb of a "hello world" pie binary.
Updates #6853
Fixes #40795
Change-Id: I3cc57c3b64f61187550bc8751dfa085f106c8475
Reviewed-on: https://go-review.googlesource.com/c/go/+/264459
Trust: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Austin Clements <austin@google.com>
Diffstat (limited to 'src/cmd')
| -rw-r--r-- | src/cmd/go/go_test.go | 33 | ||||
| -rw-r--r-- | src/cmd/link/internal/ld/lib.go | 3 |
2 files changed, 33 insertions, 3 deletions
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go index 1fb1325519..7bbadd3974 100644 --- a/src/cmd/go/go_test.go +++ b/src/cmd/go/go_test.go @@ -9,6 +9,7 @@ import ( "debug/elf" "debug/macho" "debug/pe" + "encoding/binary" "flag" "fmt" "go/format" @@ -2129,6 +2130,38 @@ func testBuildmodePIE(t *testing.T, useCgo, setBuildmodeToPIE bool) { if (dc & pe.IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE) == 0 { t.Error("IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE flag is not set") } + if useCgo { + // Test that only one symbol is exported (#40795). + // PIE binaries don´t require .edata section but unfortunately + // binutils doesn´t generate a .reloc section unless there is + // at least one symbol exported. + // See https://sourceware.org/bugzilla/show_bug.cgi?id=19011 + section := f.Section(".edata") + if section == nil { + t.Fatalf(".edata section is not present") + } + // TODO: deduplicate this struct from cmd/link/internal/ld/pe.go + type IMAGE_EXPORT_DIRECTORY struct { + _ [2]uint32 + _ [2]uint16 + _ [2]uint32 + NumberOfFunctions uint32 + NumberOfNames uint32 + _ [3]uint32 + } + var e IMAGE_EXPORT_DIRECTORY + if err := binary.Read(section.Open(), binary.LittleEndian, &e); err != nil { + t.Fatalf("binary.Read failed: %v", err) + } + + // Only _cgo_dummy_export should be exported + if e.NumberOfFunctions != 1 { + t.Fatalf("got %d exported functions; want 1", e.NumberOfFunctions) + } + if e.NumberOfNames != 1 { + t.Fatalf("got %d exported names; want 1", e.NumberOfNames) + } + } default: panic("unreachable") } diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go index 73e0b35bc0..735b84d37d 100644 --- a/src/cmd/link/internal/ld/lib.go +++ b/src/cmd/link/internal/ld/lib.go @@ -1320,9 +1320,6 @@ func (ctxt *Link) hostlink() { case objabi.Hdarwin, objabi.Haix: case objabi.Hwindows: argv = addASLRargs(argv) - // Work around binutils limitation that strips relocation table for dynamicbase. - // See https://sourceware.org/bugzilla/show_bug.cgi?id=19011 - argv = append(argv, "-Wl,--export-all-symbols") default: // ELF. if ctxt.UseRelro() { |